function getAppVersion() {
  appname= navigator.appName;
  appversion = navigator.appVersion;
  majorver = appversion.substring(0, 1); 
  if ( (appname == "Netscape") && ( majorver >= 3 ) ) return 1;
  if ( (appname == "Microsoft Internet Explorer") && (majorver >= 4) ) return 1;
  return 0;
}
function swtch(num, imgname) {
  if (getAppVersion()) {
    document[imgname].src = img[num].src;
   }
}
imgsrc = new Array();

imgsrc[1] = "img/foto/s1b.jpg";
imgsrc[2] = "img/foto/s1.jpg";
imgsrc[3] = "img/foto/s2b.jpg";
imgsrc[4] = "img/foto/s2.jpg";
imgsrc[5] = "img/foto/s3b.jpg";
imgsrc[6] = "img/foto/s3.jpg";
imgsrc[7] = "img/foto/s4b.jpg";
imgsrc[8] = "img/foto/s4.jpg";
imgsrc[9] = "img/foto/s6b.jpg";
imgsrc[10] = "img/foto/s6.jpg";
imgsrc[11] = "img/foto/s5b.jpg";
imgsrc[12] = "img/foto/s5.jpg";


if (getAppVersion()) {
  img = new Array();
  for (i = 0; i < imgsrc.length; i++) {
    img[i] = new Image();
    img[i].src = imgsrc[i];
  }
}